1. Field of the Invention
The present invention relates to a disk apparatus and can be applied to, for example, a removable hard disk apparatus for recording a video signal. It is intended to make it possible to access a data area with a short waiting time and use, as effective data, so far recorded data even at the occurrence of an abnormal termination, by storing, in a nonvolatile memory, at least address information that is necessary for access of an input data recording area of a disk-shaped-recording medium.
2. Description of the Related Art
Conventionally, among apparatuses for recording a video signal, video tape recorders using a magnetic tape as a recording medium are widely used. In such video tape recorders, a video signal and an audio signal that are input in time series are helically recorded on a magnetic tape in units of the field or frame of the video signal.
In recent years, apparatuses for recording a video signal and an audio signal using an optical disc have been proposed. Such apparatuses using an optical disc can record a video signal and an audio signal of about 2 hours.
In contrast, personal computers record application programs etc. by using a hard disk drive. In recent years, hard disk drives have been miniaturized and increased in recording density at high speeds.
In such hard disk drives, the recording area of hard disks is divided into a system entry area and a data area. Various data that are input from external apparatuses are recorded in the data area and data that are necessary for access of the data area are recorded in the system entry area.
Therefore, in hard disk drives, the contents of the system entry area are updated upon completion of data recording in the data area. This makes it possible to access recorded data by searching the system entry area and to record desired data by detecting a free region by searching the system entry area.
Incidentally, it is considered that a compact recording apparatus capable of long-time recording of a video signal could be constructed by using a hard disk drive. In this case, it is conceivable to deal with, as files, a video signal and an audio signal to be recorded in the hard disk drive and to use, as it is, a file management system that is used in personal computers.
However, where a video signal etc. are recorded simply by using a file management system that is applied to personal computers etc., there are problems that the waiting time until access of the data area is long and that it is difficult to cope with an abnormal termination of recording.
Specifically, in hard disk drives, in recording or reproduction, it is necessary to access the system entry area in advance because the data area is accessed based on data recorded in the system entry area. Hard disk drives have a problem that a long waiting time is needed until the start of access to the data area because considerable time is required for magnetic head seeking and hard disk rotation waiting in accessing the system entry area.
As for the above problem, in applying a hard disk drive to a personal computer, adverse influences of such a long waiting time can be avoided by performing a data exchange in such a manner that the personal computer side is rendered in a standby state by means of an interface between the hard disk drive and the personal computer. However, in the case of dealing with a video signal, it is necessary to record or reproduce high-transfer-rate data on a real-time basis. If the waiting time is long, there may occur an event that continuous data cannot be recorded in a case where a hard disk drive is applied to a video-camera-incorporated recording apparatus, for example.
In hard disk drives, repeated recording and erasing operations cause continuous data to be recorded in discrete regions (divided regions), as a result of which a video signal may not be produced continuously in reproduction.
On the other hand, in applying a hard disk drive to, for example, a video-camera-incorporated recording apparatus, consideration should be given to the fact that the power may be shut off during recording due to a drop, running out of electricity of a battery, a sudden power shutoff by a user, or the like. In conventional hard disk drives, it is difficult to update the contents of the system entry area at the occurrence of such an abnormal termination; a video signal that has been recorded so far with much effort cannot be used anymore.